Problem: Subtract.
There are many ways to solve this problem. Let's see two ways we can solve it. Place Value We can think in terms of hundredths: $\begin{aligned} &\phantom{=}67.89 - 9\\\\ &=67.89-9.00\\\\ &=6{,}789\text{ hundredths} -900\text{ hundredths}\\\\ &=5{,}889\text{ hundredths}\\\\ &=58.89 \end{aligned}$ Place value table Let's line up the numbers by their decimal places. Tens Ones $.$ Tenths Hundredths ${6}$ ${7}$ $.$ ${8}$ $9$ $9$ $.$ ${0}$ $0$ Now, let's subtract each place value column. Tens Ones $.$ Tenths Hundredths $\overset{5}{\cancel{6}}$ $\overset{17}{\cancel{7}}$ $.$ ${8}$ ${9}$ $-$ $9$ $.$ ${0}$ $0$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $5$ $8$ $.$ $8$ $9$ $58.89 = 67.89- 9$